Abstract
In combined therapy, time sequence and time interval of the two kinds of treatment must be in mind. Mechanism of these action is not similar, accordingly cell cycle dependent sensitivity and cell group affected should be different. MTX (0.04mg) and irradiation (200R) were administered to solid tumor growing in Donryu rat by inoculation of Yoshida ascites tumor cells. Various combination of the two treatments were administered in respect to their order and interval. DNA synthesis rate and change of radioactivity in both periphery and center of solid tumor treated by MTX administration or irradiation were studied by 125I-UdR labelling.
As the results, combined effects were in the order 1) administration of MTX on 3 days after irradiation, 2) simultaneous administration, 3) irradiation on 3 days after administration of MTX. On the other hand, the radioactivity of treated tumors in periphery or center were different in comparison with nontreated tumor. From these points, tumor cells might be not homogenous in solid tumor.
These suggested that in fractional course of administration in combined therapy, simultaneous use was practicable, because daily irradiation and 2 times a week of the drug in clinical use could not demand the time sequence of the two treatments.
